Objective lens for projecting and detecting light

Abstract

The invention relates to an objective lens for projecting and detecting light, said objective lens comprising: a microscanner (1) for variably deflecting at least one light beam (2) by means of a scanner mirror (11) that is capable of vibrating in at least one dimension and that has an optical axis (O) with respect to a rest position of the scanner mirror (11) and an opening (12) around the optical axis (O) for the collinear passage of the light beam (2); a convex mirror (3) which is arranged on the optical axis (O) and is designed to reflect the light beam (2), that is passing through the opening (12) of the scanner mirror (11), along the optical axis (O) onto the scanner mirror (11); and a lens arrangement (4) which is positioned between the convex mirror (3) and the microscanner (1) on the optical axis (O) in order to influence the divergence of the light beam (2) such that the light beam deflected by the scanner mirror (11) is collimated.

Description

[0001] Lens for projecting and detecting light

[0002] The invention relates to a lens for projecting and detecting light, which can be used in particular in augmented reality glasses (AR glasses for short), head-up displays or sensor and camera applications.

[0003] In the applications mentioned, a lens with a microscanner (also known as a microelectromechanical system, or MEMS for short) can be used to project or collect light. For projection, a light beam generated by a light source located, for example, in the temple of a pair of glasses and subsequently shaped, is directed onto the microscanner. The light beam can then be scanned by the microscanner, creating an image in an observation field. Such an imaging system with a microscanner requires comparatively few optical elements, allowing for the realization of small and cost-effective projectors.

[0004] A microscanner is described, for example, in DE 10 2021 1 16 151 B3. The microscanner disclosed therein can perform simultaneous rotational oscillations around two resonant oscillation axes in order to create a nonlinear Lissajous projection into an observation field by deflecting a light beam incident on a deflection element during the oscillations.

[0005] The oscillations scan a field of view (FOV) at high frequencies in a scan pattern resembling a Lissajous figure. Unlike conventional raster scanning methods, which periodically scan the FOV from top to bottom at maximum resolution, this allows hundreds of partial images to be processed simultaneously, enabling smoother motion representation. Furthermore, artifacts in the three-dimensional perception of fast-moving objects are greatly reduced.

[0006] In W. Davis et al., "MEMS-based pico projector display", published in IEEE / LEOS International Conference on Optical MEMs and Nanophotonics, Volume 2008, pp. 31-32, published in 2008, a MEMS projector is described in which light beams in an illumination beam path are reflected via a beam splitter onto a microscanner. The projection beam path is transmitted through the same beam splitter. Thus, the illumination and projection beam paths have only a small overlap, and the light source is arranged independently of the other components of the projector. This requires a separate beam guide for each of the light beams.

[0007] Lenses are often integrated into optics or beam paths in such a way that at least one light beam hits the microscanner at an angle, i.e., not perpendicular to the microscanner in its rest position. This is disadvantageous, among other things, because it limits the field of view angle in a projection plane that runs parallel to a mirror plane of the microscanner in its rest position. Furthermore, the oblique incidence of the light beam creates distortion. This distortion must subsequently be corrected. Furthermore, the oblique incidence of the light limits the available installation space for additional components, such as apertures, because the microscanner must be deflected further to scan the same space when the light is incident at an angle.

[0008] The object of the invention is therefore to provide a novel lens for projecting and detecting light that requires very little installation space and can be manufactured very cost-effectively using a wafer-based design. Furthermore, the object of the invention is to provide a MEMS projection device, augmented reality glasses, and a camera, each containing a lens according to the invention.

[0009] The object is achieved by an objective for projecting and detecting light, comprising a microscanner for the variable deflection of at least one light beam by means of a scanner mirror which is capable of oscillation in at least one dimension and which has an optical axis related to a rest position of the scanner mirror and an opening around the optical axis for the collinear passage of the light beam, a convex mirror which is arranged on the optical axis and is designed to reflect the light beam transmitted through the opening of the scanner mirror along the optical axis onto the scanner mirror, and a lens arrangement which is arranged between the convex mirror and the microscanner on the optical axis in order to influence a divergence of the light beam such that the light beam deflected by the scanner mirror is collimated.

[0010] Because the microscanner, convex mirror, and lens assembly are arranged on the optical axis, the lens requires very little space and can be manufactured very cost-effectively using a wafer-based design. Wafer-level assembly refers to a technology in which parts or components are mounted directly onto a wafer. A wafer is a disc of semiconductor material, such as silicon. Wafer-level assembly offers several advantages over conventional chip assembly. By performing the assembly process at the wafer level, production time and costs can be significantly reduced.

[0011] For the purposes of the invention, a system is considered capable of oscillation if it is capable of performing a periodic movement around a rest position. Thus, any system capable of performing a periodic movement around a rest position in several dimensions is capable of oscillation in multiple dimensions.

[0012] The scanner mirror preferably has a diameter of 0.5 mm to 10 mm and is preferably round. The opening advantageously has a diameter of 20 μm to 1,000 μm and is advantageously round. The convex mirror preferably has a diameter of 0.5 mm to 10 mm, or the same diameter as the scanner mirror or only slightly larger than the scanner mirror, and is preferably round. The lens arrangement preferably has a thickness of 0.5 mm to 10 mm and a diameter of 3 mm to 20 mm.

[0013] Preferably, the scanner mirror and / or the aperture have a diameter between 0.1 mm and 5 mm. Particularly preferably, the scanner mirror 11 and / or the aperture have a diameter between 1 mm and 2 mm. Preferably, the distance between the scanner mirror and the aperture is less than 1 mm, particularly preferably the distance between the scanner mirror 11 and the aperture 7 is less than 0.5 mm and more than 0.1 mm. Preferably, the angle by which the scanner mirror can be tilted relative to its rest position is between 3° and 15°, particularly preferably between 5° and 10°.

[0014] Additional optical elements, such as lenses or diffractive optical elements, can be arranged between the lens arrangement and the convex mirror or between the lens arrangement and the microscanner to influence the divergence of the at least one light beam and / or to minimize or eliminate imaging errors. Preferably, at least one aperture is provided in the beam path of the light beam, which aperture is mounted in a defined position relative to the microscanner depending on the direction of incidence of the light beam to limit the light beam.

[0015] An optical aperture is a mechanical component that controls the amount of incident light in an optical system and / or spatially limits a light beam. It is a round, oval, or polygonal opening, for example, that is embedded in an aperture material. The aperture material can be metal or plastic, for example. The aperture can be incorporated into the lens, particularly through wafer-level assembly. The aperture can also be created by a structured coating with an absorbing material or an absorbing surface structure on a transparent substrate.

[0016] Advantageously, at least the scanner mirror is arranged within an encapsulation which hermetically encloses the scanner mirror and the encapsulation has an interior with a gas pressure which is reduced compared to normal conditions.

[0017] The encapsulation of the microscanner is intended to protect the moving mechanical and optical components of the microscanner and to shield it from external influences and contamination. Placing the microscanner in a vacuum serves to reduce friction, avoid airborne particles, and mitigate thermal effects such as heat input through convection.

[0018] The microscanner can be designed, in particular, as a micro-electro-mechanical system (MEMS) and / or configured to effect a nonlinear Lissajous projection into an observation field. The microscanner is configured to scan the light beam across the observation field, thereby generating an image in the observation field. By scanning the at least one light beam along a Lissajous figure, hundreds of partial images can be processed simultaneously, enabling a smoother motion representation. Furthermore, the user's perception of artifacts in the three-dimensional representation of fast-moving objects is greatly reduced.

[0019] The lens arrangement preferably comprises one or more planar optical elements with a diffractive effect. Likewise, the lens arrangement may preferably contain one or more elements consisting of an optical metamaterial. Alternatively or additionally, the lens arrangement may comprise one or more metal lenses or one or more refractive optical lenses.

[0020] The objective advantageously comprises at least one light source for emitting the at least one light beam along the optical axis in the direction of the microscanner, and the at least one light source is arranged on the side of the microscanner facing away from the convex mirror. If the objective comprises a light source, it can be used, in particular, as a projection device to effect a projection into an observation field.

[0021] Preferably, the at least one light source is equipped with a collimating or converging beam shaping device. The divergence with which the light beam is emitted determines how the remaining components of the objective, in particular the microscanner, the aperture of the microscanner, and the convex mirror, are dimensioned and arranged. Therefore, it is advantageous if the divergence of the light beam is adjustable after it has been emitted by the light source.

[0022] Advantageously, the at least one light source is a laser diode configured as an edge emitter, a surface emitter, or a fiber-coupled laser light source equipped with beam shaping and focusing. Surface emitters and fiber-coupled light sources have the advantage that the light beams emitted by these light sources are generally less divergent than those emitted by edge emitters. However, the acquisition costs of surface emitters and fiber-coupled light sources are generally significantly higher than those of edge emitters.

[0023] The lens can preferably comprise at least one sensor for detecting the at least one light beam, and the at least one sensor can be arranged on the side of the microscanner facing away from the convex mirror. If the lens comprises a sensor, it can be used with different types of detectors, such as cameras (CCD, CMOS), position-sensitive or conventional photodiodes, quadrant photodiodes, or photodiode arrays.

[0024] The problem is further solved by a MEMS projection device containing a lens according to one of the described embodiments. The problem is also solved by augmented reality glasses containing a lens for generating and displaying images according to one of the described embodiments, wherein the at least one light source for emitting the at least one light beam is integrated into the lens or the augmented reality glasses.

[0025] The object is further achieved by a camera comprising a lens according to one of the described embodiments and at least one sensor for detecting the at least one light beam.

[0026] The invention will be described in more detail below by means of exemplary embodiments based on the drawings. These show:

[0027] Fig. 1 a A view of a first embodiment of the objective with a light source, a microscanner, a lens arrangement comprising a lens and a convex mirror and a first section of a beam path,

[0028] Fig. 1 b is a view of the first embodiment of the lens and a second section of the beam path,

[0029] Fig. 1 c a view of the first embodiment of the lens and a third section of the beam path,

[0030] Fig. 2 is a side view of a section through a second embodiment of the lens, wherein the lens arrangement contains only one metal lens,

[0031] Fig. 3 is a side view of a section through a third embodiment of the lens, showing two different beam paths of the light beam after it has been deflected by the microscanner, and the lens arrangement includes a converging lens and a diverging lens,

[0032] Fig. 4 is a side view of a section through a fourth embodiment of the lens, wherein an aperture is arranged directly above the microscanner, and

[0033] Fig. 5 is a side view of a section through a fifth embodiment of the lens, wherein an aperture is arranged directly above the microscanner and the scanner mirror is completely enclosed by encapsulation. Fig. 1a shows a first embodiment of a lens for projecting and detecting light. The lens comprises a microscanner 1 for the variably deflection of a light beam 2. The microscanner 1 comprises a scanner mirror 11 that is capable of oscillation in one dimension for deflecting the light beam. The scanner mirror 11 has an optical axis O related to a rest position of the scanner mirror 11 and an opening 12 around the optical axis O for the collinear passage of the light beam 2.

[0034] The lens further comprises a convex mirror 3. The convex mirror 3 is arranged on the optical axis O and is designed to reflect the light beam 2 transmitted through the opening 12 of the scanner mirror 1 1 along the optical axis O onto the scanner mirror 1 1.

[0035] In addition, the objective comprises a lens arrangement 4. The lens arrangement is arranged between the convex mirror 3 and the microscanner 1 on the optical axis O and is designed to influence a divergence of the light beam 2 such that the light beam deflected by the scanner mirror 11 is collimated.

[0036] Fig. 1 a shows a first section of a beam path of the light beam 2. The light beam 2 is emitted by a light source 6 in the direction of the microscanner 1 and transmitted through the opening 12 of the microscanner 1. Between the microscanner 1 and the convex mirror 3, the light beam 2 converges at a focus and is transmitted through the lens arrangement 4, whereby the divergence of the light beam 2 decreases before it strikes the convex mirror 3. The distances and dimensions of the scanner mirror 1 1 , opening 12, convex mirror 3 and lens arrangement 4 must be coordinated such that a diameter of the light beam 2 at the convex mirror 3 is not larger than the diameter of the convex mirror 3, since otherwise a portion of the light beam would be lost upon reflection at the convex mirror.

[0037] Fig. 1 b shows the first embodiment of the objective lens and a second section of a beam path of the light beam 2. The light beam 2 is reflected by the convex mirror 3 in the direction of the microscanner 1. Before the light beam 2 strikes the microscanner 1, it is transmitted again through the lens arrangement 4, whereby the divergence of the light beam 2 further decreases. The light beam 2 then strikes the microscanner 1. The light beam 2 is deflected by the microscanner 1 in the direction of the optical axis O, as shown in Fig. 1 c. In the process, an initial portion of the light beam 2 is always lost at the microscanner 1 due to the opening 12. After it has been deflected by the microscanner 1, the light beam 2 is transmitted a third time through the lens arrangement 4 and is thereby collimated.Depending on the dimensions and arrangement of the convex mirror 3 and depending on the direction in which the light beam 2 has been deflected by the microscanner 1, a second portion of the light beam 2 is also lost at the convex mirror 3.

[0038] A lens arrangement 4 containing only one metal lens is shown in Fig. 2. In the second embodiment of the objective shown in Fig. 2, the metal lens of the lens arrangement 4 is arranged in the same plane as the convex mirror 3. For this purpose, a recess is provided in the metal lens in which the convex mirror 3 is arranged. Fig. 2 shows the entire beam path of the light beam 2 from the light source 6 until the light beam 2 passes through the metal lens. In the second embodiment, the light beam 2 is transmitted only once through the lens arrangement 4 and is thus collimated.

[0039] The lens arrangement 4 can also consist of several lenses, for example, a converging lens 41 and a diverging lens 42, as in the second embodiment shown in Fig. 3. The interaction of the converging lens 41 and the diverging lens 42 collimates the deflected light beam 2. In the configuration shown in Fig. 3, the scanner mirror 11 of the microscanner 1 is deflected in one configuration, and the deflected light beam 2 does not run along the optical axis O. This configuration is represented in Fig. 3 by dashed lines.

[0040] Fig. 4 shows a fourth embodiment of the lens. The fourth embodiment of the lens comprises a sensor 5. The sensor 5 is arranged below the microscanner 1, as seen from the direction of incidence of the light beam 2. The incident light beam 2 is reflected or deflected by the microscanner 1 onto the convex mirror 3 and then reflected by the convex mirror 3 through the microscanner 1 onto the sensor 5.

[0041] In addition, the fourth embodiment has an aperture 7 located between the microscanner 1 and the lens arrangement 4 for limiting the light beam 2. The aperture 7 must be dimensioned and arranged such that the scanner mirror 11 does not come into contact with the aperture 7 during its deflection. Preferably, the scanner mirror 11 and / or the aperture 7 have a diameter between 0.1 mm and 5 mm. Particularly preferably, the scanner mirror 11 and / or the aperture have a diameter between 1 mm and 2 mm. Preferably, the distance between the scanner mirror 11 and the aperture 7 is less than 1 mm, particularly preferably the distance between the scanner mirror 11 and the aperture 7 is less than 0.5 mm and more than 0.1 mm. Preferably, the angle by which the scanner mirror 11 can be tilted relative to its rest position is between 3° and 15°, particularly preferably between 5° and 10°.

[0042] Fig. 5 shows a side view of a section through a fifth embodiment of the lens. A diaphragm 7 is arranged directly above the microscanner 1, and the microscanner 1 is completely enclosed by an encapsulation 8. Furthermore, the scanner mirror 11 is arranged within an encapsulation 8, which hermetically encloses the scanner mirror 11 together with the microscanner 1. An interior of the encapsulation 8 has a gas pressure that is reduced compared to normal conditions.

[0043] List of reference symbols

[0044] 1 micro scanner

[0045] 11 scanner mirrors

[0046] 12 Opening 2 light beams

[0047] 3 convex mirrors

[0048] 4 lens arrangement

[0049] 41 first lens

[0050] 42 second lens 5 sensor

[0051] 6 Light source

[0052] 7 aperture

[0053] 8 Encapsulation O Optical axis

Claims

Patent claims 1 . Lens for projecting and detecting light, comprising - a microscanner (1) for the variable deflection of at least one light beam (2) by means of a scanner mirror (11) which is capable of oscillation in at least one dimension and which has an optical axis (O) related to a rest position of the scanner mirror (11) and an opening (12) around the optical axis (O) for the collinear passage of the light beam (2), - a convex mirror (3) arranged on the optical axis (O) and designed to reflect the light beam (2) transmitted through the opening (12) of the scanner mirror (11) along the optical axis (O) onto the scanner mirror (11), and - a lens arrangement (4) arranged between the convex mirror (3) and the microscanner (1) on the optical axis (O) to influence a divergence of the light beam (2) such that the light beam deflected by the scanner mirror (11) is collimated.

2. Lens according to claim 1, wherein in the beam path of the light beam (2) there is at least one aperture (7) mounted in a defined relative position to the microscanner (1) as a function of a direction of incidence of the light beam (2) for limiting the light beam (2).

3. Lens according to one of claims 1 to 2, wherein at least the scanner mirror (11) is arranged within an encapsulation (8) which hermetically encloses the scanner mirror (11) and has an interior with a gas pressure reduced compared to normal conditions.

4. Lens according to one of claims 1 to 3, wherein the microscanner (1) is designed as a microelectromechanical system (MEMS).

5. Lens according to one of claims 1 to 4, wherein the microscanner (1) is designed to effect a non-linear Lissajous projection into an observation field.

6. Lens according to one of claims 1 to 5, wherein the lens arrangement (4) comprises one or more compound optical lenses.

7. Lens according to one of claims 1 to 5, wherein the lens arrangement (4) comprises one or more planar optical elements with a diffractive effect.

8. Lens according to one of claims 1 to 5, wherein the lens arrangement (4) contains one or more elements consisting of optical metamaterial.

9. Lens according to one of claims 1 to 8, wherein the lens comprises at least one light source (6) for emitting the at least one light beam (2) along the optical axis (O) in the direction of the microscanner (3) and the at least one light source (6) is arranged on the side of the microscanner (1) facing away from the convex mirror (3).

10. Lens according to claim 9, wherein the at least one light source (6) is equipped with a collimating or converging beam forming device.

11. Lens according to claim 9, wherein the at least one light source (6) is designed as an edge emitter, a surface emitter or a fiber-coupled light source.

12. Lens according to one of claims 1 to 8, wherein the lens comprises at least one sensor (5) for detecting the at least one light beam (2) and the at least one sensor (5) is arranged on the side of the microscanner (1) facing away from the convex mirror (3).

13. A MEMS projector comprising a lens according to any one of claims 1 to 12.

14. Augmented reality glasses, comprising a lens for generating and displaying images according to one of claims 1 to 11, wherein the at least one light source (6) for emitting the at least one light beam (2) is integrated in the lens or in the augmented reality glasses.

5. Camera comprising a lens according to one of claims 1 to 8 and at least one sensor (5) according to claim 12 for detecting the at least one light beam

Images